DESCRIPTION: This is a follow-up study of the relationship between airborne acidic air pollutants and the respiratory health of approximately 3300 late adolescent children living in 15 communities in the U.S. and Canada, in whom respiratory symptoms and pulmonary function had been previously measured, at ages 8-11. The air pollution monitoring program produced measures of annual and Summer average hydrogen ion concentrations, and comparable measures of size-fractionated particulate concentrations, SO2, NO2, and O3. These measurements showed a 20-fold range of acid aerosol levels across communities. The health examinations showed correlations with measures of pulmonary function (including forced expiratory volumes (FEV1, FEV.75), forced vital capacity (FVC)), and measures of flow at low lung volumes. There are four Aims: 1) to see whether children raised in regions with higher levels of acid aerosol have lower levels of lung function at maturation than children raised in cleaner environments; 2) to see whether pulmonary function tracks between ages 8-11 and 17-18, and whether this tracking is related to acid aerosol exposure; 3) to determine whether initiation of cigarette smoking affects respiratory symptoms and pulmonary function independently of or interactively with acid aerosol exposure; and 4) to assess whether incidence or severity of asthma is affected by those exposures.